1. Field of the Invention
The present invention relates to the manufacturing of large format Lithium cells for battery packs.
2. Brief Description of the Related Art
It is a known problem in the manufacturing of Lithium cells for battery packs that the Lithium cells should contain only a minimum of water, as water leads to corrosion and side reactions which in turn can lead to a loss in performance of the respective cells, such as capacity loss, missing power capability, etc.
The water content in a Lithium cell should normally be less than 30 ppm. Generally, this is achieved by handling the materials and processes under strictly dry conditions. Machinery and materials are brought into dry rooms with reduced humidity. However, the construction and maintenance of full size dry rooms that are capable of receiving the necessary manufacturing equipment is very cost intensive.
Another problem with dry rooms is that the staff, necessary to operate the manufacturing machinery, must be able to enter and leave the dry room, without interfering with the dry room conditions, just as the material necessary for the manufacturing process must be brought into the dry room. The human body carries substantial quantities of humidity into those dry rooms. Once opened, e.g. for bringing in machinery, materials or people, it takes a long time to reach Lithium working conditions again, which is contra productive and makes the whole process very costly. Furthermore, the humidity can lead to difficulties in controlling the manufacturing processes and thus to lower grade products. It also leads to more difficult working conditions for employees who are exposed to extreme dry conditions for prolonged periods of time.
What has been proposed to solve the above mentioned problems is that materials for lithium cell manufacturing are pre-dried before they are brought into the dry rooms, which reduces the amount of humidity entered. However, this doesn't solve the general problem that arises from the fact that very large dry room volumes must be created and maintained.
Accordingly, there is still a need to provide a solution for the manufacturing of large format Lithium cells that effectively overcomes the above mentioned problems.